Heat exchanger utilizing products of combustion as a heating medium



Dec. 6, 1955 H. WALTER I HEAT EXCHANGER UTILIZING PRODUCTS OF COMBUSTIONAS A HEATING MEDIUM '7 Sheets-Sheet 1 Filed March 7, 1952 ZOFFUWZ ZOUMKOLZKMZ w UWm KUICQWI DUNZM JUDK HELLMUTH WALTER mmkamlmmm K71INVENTOR.

Dec. 6, 1955 H. WALTER HEAT EXCHANGER UTILIZING PRODUCTS OF COMBUSTIONAS A HEATING MEDIUM 7 Sheets-Sheet 2 Filed March 7, 1952 FIG.2

IN VEN TOR.

HELLMU TH WALTER Dec. 6, 1955 H. WALT HEAT EXCHANGER UTILIZI COMBUSTIONAS A HEATING MEDIUM Filed March 7, 1952 EHEATED AIR NG PRODUCTS 0F 7Sheets-Sheet 3 HELLMUTH WALTER IN V EN TOR.

Dec. 6, 1955 H. WALTER HEAT EXCHANGER UTILIZING PRODUCTS OF COMBUSTIONAS A HEATING MEDIUM 7 Sheets-Sheet 4 Filed March 7, 1952 FIG. 6

INVENTOR.

H ELLMUTH WALTER Dec. 6, 1955 H. WALTER HEAT EXCHANGER UTILIZINGPRODUCTS OF COMBUSTION AS A HEATING MEDIUM 7 Sheets-Sheet 5 Filed March7, 1952 FUEL GAS EJ'ECTOR INVENTOR.

ELLMUTH WALTER E TECTOR EXHAUST HOT GAS COLD GAS FIG] Dec. 6, 1955 H.WALTER HEAT EXCHANGER UTILIZING PRODUCTS OF COMBUSTION AS A HEATINGMEDIUM '7 Sheets-Sheet 6 Filed March 7, 1952 FIGJO INVENTOR.

H ELLM UTH WALTER Dec. 6, 1955 H. WALTER 2,725,873

HEAT EXCHANGER UTILIZING PRODUCTS OF COMBUSTION AS A HEATING MEDIUMFiled March 7, 1952 7 Sheets-Sheet 7 FUEL GAS 99 l 98 93 aw? HEATER x 949 a ,9, H, f4 I j ff h I03 l we 97 /4 |O| A EXHAUST l if; x I04- F I 86l 9 3? H 9 05 5 8 g s| 95 t a l I 96 10s 89 L 8 -95 1 5 AIR I02 38 TO 84TURBINE 92 90 9| 83 FROM O COMPRESSOR H0 8 IZI H4- TO PlPE LINE j PREG-ENERATQR INVEN TOR.

GUI-.

FROM TURBINE EXHAUST United States Patent HEAT EXCHANGER UTILIZINGPRODUCTS 0F CONIBUSTION AS A HEATING MEDIUM Hellmuth Walter, UpperMontclair, N. J., assignor to Worthington Corporation, Harrison, N. J.,a corporation of Delaware Application March 7, 1952, Serial No. 275,30516 Claims. 01. 126-109) This invention relates to heat exchangers andmore particularly to a fuel fired heater wherein the medium to be heatedis circulated through heat exchange tubes countercurrent to hot gasesproduced by combustion of fuel in the shell containing the tubes.

The fuel fired heater or heat exchanger of the present invention isparticularly adaptable for use in a gas or vapor compression unit forcompressing flowing gases or vapor in an isolated system or unit,wherein the energy required for compression is derived from the heat ofcombustion of fuel burned in one of the components of the system asdisclosed in my copending applications, Serial No. 181,512, filed August25, 1950, and Serial No. 257,303, filed March 7, 1952. However, the heatexchanger or fuel fired heater of the present invention is not limitedto such use, the present invention being limited to the fuel firedheater or exchanger per se, which may be adapted to any use wherepractical.

An object of the present invention is to provide for a heat exchangerwhich provides for countercurrent flow of gases, that is, of the heatingand heated mediums insuring the highest permissible value of meantemperature difference and least area of heat transfer surface, and toprovide for minimum loss of pressure of the gases with a given value ofoverall conductance by flow of the gas longitudinally of the heattransfer surfaces with least practical changes in flow direction. Afurther object is to insure by recirculation of a part of thecooled-down combustion gases, that the highest permissible meantemperature difference is not exceeded.

' With these and other objects in view, as may appear from theaccompanying specification, the invention consists of various featuresof construction and combination of parts, which will be first describedin connection with the accompanying drawings, showing a heat exchangerutilizing products of combustion as a heating medium of a preferred formembodying the invention, and the features forming the invention will bespecifically pointed out in the claims.

In the drawings:

Figure l is a diagrammatic layout of a gas or vapor compressing unitshowing one application of the heat exchanger or heater.

Figure 2 is a side elevation of one form of the heat exchanger orheater.

Figure 3 is a horizontal section through the heat exchanger of Figure 1taken on the line 3-3 of Figure 4.

Figure 4 is a vertical section taken on the line 44 of Figure 3.

Figure 5 is a side elevation of another form of the heat exchanger orheater.

Figure 6 is a horizontal section through the heat exchanger or heatershown in Figure 5 and taken on the line 6-6 of Figure 7.

Figure 7 is a vertical section taken on the line 77 of Figure 6. I

Figure 8 is a side elevation of still another form of the heat exchangeror heater.

2,725,873 Patented Dec. 6, 1955 ice Figure 9 is a horizontal sectionthrough the heat exchanger or heater of Figure 8 and taken on the line9-9 of Figure 11.

Figure 10 is a horizontal section through the heat ex. changer or heatertaken on the line 10-10 of Figure 11, an

Figure 11 is a vertical section through the heat exchanger or heatershown in Figure 8.

Figure 1 of the drawings shows a diagrammatical layout of a compressingunit for compressing flowing gas or vapor and generically the systemincludes a line pipe 1 through which the flowing gas or vapor to becompressed flows. The gas or vapor is taken from line 1, through a pipe2 and delivered to the suction of a compressor 3. Part of the gas fromthe pipe 2 is extracted through an extraction pipe 4 and passes throughone or more regenerators shown at 5, after which it passes into the fuelfired heater or heat exchanger 6 which constitutes the presentinvention. The heated extracted gas is delivered from the fuel firedheater or heat exchanger 6 through a pipe 7 to a turbine 8 which drivesthe compressor 3. The compressed gas is returned to the pipe line 1through a suitable connection 9. This compressing unit is specificallydisclosed and claimed in my companion application, Serial No. 275,301,filed March 7, 1952 and Serial No. 275,302, also filed March 7, 1952,and is shown herein and described generically merely for the purpose ofshowing one use of the heat exchangers forming the subject matter of thepresent invention.

In Figures 2 to 4 inclusive of the drawings, the fuel fired heatexchanger is illustrated as including a shell 10 which is preferablycylindrical in shape. The lower end of the shell 10 is enclosed by aclosure head 11 which is, in the main, preferably formed of heatinsulating material and the opposite end of the shell 10 is enclosed bya removable head 12.

A pair of doughnut shaped tubular rings 13 and 14 are carried by theclosure 11 Within the shell of the heat exchanger and the ring 13'has aninlet 15 for the gas or vapor to be heated communicating therewith,while the ring 14 has an outlet 16 for the heated gas'or vapor.

An annular or circular partition 17 is located within the shell 10 andextends from the closure 11 to the inner surface 18 of the heatinsulating filler 19 of the removable head 12 forming a centralcombustion chamber 20 and an outer annular heat exchange chamber 21. Thepartition 17 is provided 'with a plurality of transverse openings 22 atits lower end, that is, the end remote from the removable head 12 whichopenings establish communicationbetween the inner chamber 20 and theouter annular chamber 21. I

A plurality of substantially inverted U-shaped heatexchange tubes 23have theirinlet ends connected to the doughnut ring 13and their outletends connected to the doughnut ring 14. The bends 24 of the tubes extendthrough the annular partition 17 as clearly shown in Fig ure 4 of thedrawings and thus one of the legs of each of the tubes 23 is located inthe central chamber 20 while the other leg is located in the annularchamber 21.

The removable head 12 is in the major portion filled with a filler ofheat insulating material shown at 19 which has a passage 25 extendingaxially therethrough and opening into the central combustion chamber 20.The passage 25 is provided for admitting air into the combustion chamberfor mixture withfuel to provide a combustible mixture within the chamber20.

In the system shown in Figure 1 of the drawings the air which isadmitted to the shell 10 through the passage 25 is preheated in an-airheater 26 although this is not necessary to the operation of the heatexchanger per se. An inlet pipe 27 for fuel gas or vapor extends intothe head 12 and axially downwardly through the opening 25 having itsoutlet end flaredas shown at 28. The air passage 25 is substantiallyVenturi shaped, that is, it de creases in cross sectional area for aportion of its length inwardly of its inlet and graduallyincreasesinarea from the point of minimum cross sectionalareato theoutlet,although the area at the outlet is of course -restricted by the flared.end 28-of the. fuel inlet pipe 27 so that the air will be deflectedinwardly and outwardly as it enters the combustion chamber 20. Asubstantially conical defiector 29 is located in the flared outlet end28 of the fuel inlet pipe for directing the fuel gas or vapor into thecornbustion chamber. As shown in Figure 4 of the drawings, ignitingmeans in the form of an ordinary spark plug 30 is provided forignitingthe mixture of fuelgas or vapor and air in the combustion chamber tocause a burning thereof. It is to be understood, however, that anysuitable type of ignition means may be provided.

The burning combustible fuelin the combustion chamber 20 passesdownwardly therein longitudinally of the inner legs of the U-shapedtubes 23 in countercurrent flow to the flow of the gas or medium to beheated through the tubes. At the bottom of the shell the products ofcombustion pass through the openings 22 into the annular outer chamber21 and pass upwardly therein longitudinally of the tubes 23 and in acountercurrent direction to the downward flow of medium to be heatedflowing through the tubes. The products of combustion exhaust from theshell 10 near the upper end thereof through a plurality ofcircumferentially spaced openings 31 in which an annular exhaust passage32 formed by a ring formed upon or attached to the outer surface of theshell 10. From the exhaust ring 32 the products of combustion exhaustthrough an outlet 33.

As is clearly shown in Figure 4 of the drawings, the closure 11 and theremovable head 12 are both detachably connected to the shell 10 so thatin case of repair or replacement of the ignition means or any of theparts carried by the head 12 the head may be removed without disturbanceof the shell 10 and the connections with the pipes and 16. Such removalof the head 12 will also permit access to the tubes 23.

The form of the invention shown in Figures 5, 6 and 7 differs in somedegree from the form of the invention shown in Figures 2 to 4 inclusive,but the principles of operation and the general principles ofconstruction are similar.

This form of the invention includes a shell 50, one end of which isclosed by a closure 51 and'the other end by a removable head 52. Tubulardoughnut rings 53 and 54 are located within the shell-and they haveinlet and outlet connections 55 and 56 respectively, connected theretofor the inlet and outlet of the medium to be heated. Heat exchange tubes57 have their inlet ends connected to the doughnut ring 53 and theiroutlet ends connected to the doughnut ring 54. The tubes 57 aresubstantially U-shaped and their bends extend through the annularpartition 58 located within the shell to provide the central combustionchamber 59 and theannular heat exchange chamber-60 with the inletupflowing legs of the U-shaped tubes located in the central combustionchamber 59 and the downflowing outlet legs of the tubes located in theheat exchange chamber 60.

In this form of the invention a second annular partition 61 is locatedwithin the shell forming an annular air passage chamber 62 to the lowerend of which air is admitted through an inlet 63. The'annular airpassage chamber 62 is closed at its bottom or at its end adjacent to thedoughnut rings 53 and 54 and its upper end is constricted as shown at 65and opens intoan annular air passage 66 formed in the removable head" 52by the passage-forming heat insulation member 67 against which the upperend of the annular-partition 58abuts. 'The annular air passage 66 opensintoan axial airpassag'e 68, the

flared' outlet endof which '.'-opens inttri-thte fcombustion chamber 59for deliveringthe-"air"to the combustion chamber. Fuel, gas or vapor isadmitted to the combustion chamber 59 for mixture with the air in thecombustion chamber through a fuel gas or vapor inlet 69 extendingaxially through the opening or passage 68. A substantially conicalspreader 70 is located in the fuel gas inlet pipe 69 with its baselocated at the outlet end of the gas inlet pipe. Fuel ignition means 71,which is shown in the form of a spark plug is carried by the spreader 70and extends into the combustion chamber 59 for igniting the mixed fuelgas or vapor and air to burn the water in the combustion chamber- 59 toprovide heat for heating the medium flowing through the tubes 57.

The annular partition 58 has openings 72 in its lower end through whichthe products of combustion pass from the combustion chamber 59 into theannular heat exchange chamber 60. The products of combustion flowupwardly through the heat exchange chamber 60 in countercurrent flowlongitudinally of the outer legs of the tubes 57 and passes out of theannular chamber 60 through a plurality of circumferentially spacedopenings 74 into an annular exhaust passage 75. The annular exhaustpassage 75 is in the form of a substantially semi-circular ring on theouter surface of the partition 61 and it has an outlet connection 76connected thereto.

The provision of the annular air passage 62 which, in effect, is aconcentric jacket, serves to cool the walls of the unit. The upperoutlet end of the annular partition 61 and the wall of the shell 50 isso constructed as to produce a jet or ejector effect as the air which isheated through the partition 61 flows upward into the annular passage66. This action picks up a small quantity of the products of combustionand stimulates recirculation of relatively cool-products of combustionand brings about a reduction in the temperature within the combustionchamber.

The form of the invention shown in Figures 8 to 11 inclusive illustratesin a single unit the combination of a fuel fired heat exchangersimilarto that disclosed in Figures 1 to 7 inclusive and a non-fuelfired heat exchanger.

This form of the invention comprises a main shell 80 which is composedof the shell 81 of the fuel fired section, the shell 82 of the non-fuelfired heat exchange section and the central connecting element 83interposed between the two shells 81 and 82.

The fuel fired heat exchange section of this form of the inventionincludes the closure plate 84 and the removable top or cover 85. Anannular partition 86 corresponding to the partitions 17 and 58, islocated within the shell 81 forming the inner combustion chamber 87 andthe outer annular heat exchange chamber 88. Of course, in all of theforms of the invention the inner combustion chambers are actually and,in effect, heat exchange chambers, as Well as the outer annularchambers. Substantially U-shaped tubes 89 are carriedby the closureplate 84 with their inlet ends opening out through the closure plate,their bends extending through the partition 86 and with their outletlegs in the heat exchange chamber 88 and their outlet ends openingthrough the closure 84 into an annular outlet passage 90 formed in thechamber within the central connecting unit 83. The central connectingunit 83 has anannular partition 91 formed therein forming a centralchamber or passage 92 in which the medium to be heated enters and fromwhich it passes into the inlet ends of the tubes 89. The removable head85 has an air passage 93 formed therein by the member or block 94 ofinsulating material. The inlet side of the air passage 93 opens into theannular air passage 95 formed within the shell 81 about the annular heatexchange passage 88 by the partition 96. As clearly shown in Figure 11of the drawings the outlet end of the annular air passage 95 isconstricted as shown at 97 and a portion of the passage 93 opens intothe annular. heat exchange chamber 88 the same as passage 66in Figure -7of the drawings opens partlyintoatheannularheat exchange chamber 60 withtheou'tletend of-the-annular air passage 62 being constricted. The airpassage 93 opens through an axial opening 98, the outlet endof which isflared into the combustion chamber 87 and the pipe 99 for inlet of fuelgas into the combustion chamber 87 is carried by the removable head 85and extends axially through the opening 98. A spreader 100 is located inthe fuel gas inlet pipe 99 and it carries suitable ignition means 101for igniting the mixture of air and gas in the combustion chamber 87.The products of combustion pass downwardly in the combustion chamber 87and through the openings 102 in the annular partition 86 into theannularheat exchange chamber 88 from which they pass throughcircumferentially spaced openings 103 into the annular exhaust passage104 and out of the passage through the outlet 105. Air is admitted tothe annular air passage 95 through an air inlet 106.

The non-fuel fired heat exchange section of the form of the inventionshown in Figures 8 to 11 includes the shell 82 having a transversepartition or end 110 which forms the lower part of the chamberintermediate the sections 81 and 82. A plurality of U-shaped tubes 111are carried by the partition 110. The inlet ends of the tubes open intothe annular inlet chamber 112 formed about the circular or annularpartition 91 and separated from the outlet passage 90 by the transversepartition 113. Theroutlet ends of the U-shaped tubes 111 open into thecentral passage 92 formed by the annular partition 91 so that the mediumto be heated which enters the annular inlet chamber 112 through theinlet 114 passes downwardly through the outermost legs of the U- shapedtubes 111 and upwardly through the inner legs into the passage 92 andfrom the passage 92 into the inlet ends of the U-shaped tubes 89. Anannular bafile 115 is located within the shell 82 and extends downwardlybetween the inlet and outlet legs of the U-shaped tubes 111. The inletpipe 116 extends axially into the shell 82 to a point near thetransverse partition 110 so that the heating medium entering the shell82 from the inlet pipe or tube 116 is deflected laterally and downwardlyby the partition 110. The laterally and downwardly flowing heatingmedium passes longitudinally along the inner legs of the tubes 111 incounter-flow direction to the flow of the medium to be heated throughthe tubes and passes around the lower end of the baffie 112 and upwardlyalong the outer inlet legs of the U-shaped tubes 111 in counter-flowdirection to the flow of the medium to be heated flowing through theselegs. The heating medium passes out of the shell 32 through a pluralityof circumferentially spaced openings 117 into an annular exhaust passage118. The exhaust passage 118, like the exhaust passages 32, 75 and 104,is formed by an arcuate annular member 120 attached to or formed uponthe outer surface of the shell 82. An outlet pipe 121 is connected tothe exhaust passage 118.

It will be understood that the invention is not to be limited to thespecific construction or arrangement of parts shown, but that they maybe widely modified with in the invention defined by the claims.

What is claimed is:

l. In a fuel fired heat exchanger, a shell having an inlet forcombustible fuel at one end thereof, an annular partition in said shellforming an inner combustion chamber and an annular outer heat exchangechamber, said inlet for combustible material communicating with saidinner combustion chamber, said annular partition having openings thereinnear the end of the shell remote from said fuel inlet, a' plurality ofsubstantially U-shaped tubes in said shell and having their inlets andoutlets at the ends of the shell remote from said fuel inlet, the bendsof said tubes extending through said annular partition whereby one legof each of the tubes will be located in said inner combustion chamberand the other leg of each tube will be located in the outer annular heatexchange chamber said shell having an outlet for gases of combustiontherein, said outlet opening into said heat exchange chamber adjacent tothe end of the shell remote from said openings in said annularpartition.

2. A fuel fired heat exchanger as claimed in claim 1 wherein said shellcomprises a central cylindrical portion open at both ends and removableclosure heads for the open ends, and wherein said inlet for combustiblefuel is carried wholly by one of said removable end closure heads.

3. A fuel fired heat exchanger as claimed in claim 1, a pair ofdoughnut-shaped tubular rings in the end of said shell remote from thefuel inlet, the inlet ends of said U-shaped tubes connected to one ofsaid rings and the outlet ends of the tubes connected to the other ofsaid rings, an inlet for fluid to be heated connected to the tubulardoughnut-ring in which the inlet ends of said tubes are connected and anoutlet for fluid to be heated connected to the tubular doughnut-ring towhich the outlets of said tubes are connected.

4. A fuel fired heat exchanger as claimed in claim 1 including a tubulardoughnut ring connecting the inlets of all of said tubes and a secondtubular doughnut ring connecting the outlets of all of said tubes, aninlet for fluid to be heated connected to said first tubular doughnutring, and an outlet for fluid to be heated connected to said secondtubular doughnut ring.

5. A fuel fired heat exchanger as claimed in claim 1 wherein the end ofsaid shell having the inlet forcom bustible fuel has an annular airpassage therein, a heat insulating member in said shell end and providedwith an axial opening opening into the inner chamber and communicatingwith said air passage to form an inlet for air to the inner chamber, afuel gas inlet pipe extending through said air inlet, means for ignitingthe fuel gas in said inner chamber, and a second annular partition insaid shell forming an air passage about said outer chamber and havingcommunication with said annular air passage in the fuel inlet end of theshell. Y

6. A fuel fired heat exchanger as claimed in claim 1 wherein the end ofsaid shell having the inlet for combustible fuel has an annular airpassage therein, a heat insulating member in said shell end and providedwith an axial opening opening into the inner chamber and communicatingwith said air passage to form an inlet for air to the inner chamber, afuel gas inlet pipeextending through said air inlet, means for ignitingthe fuel gas in said inner chamber, and a second annular partition insaid shell forming an air passage about said outer chamber and havingcommunication with said annular air passage in the fuel inlet end of theshell, a tubular doughnut ring connecting the inlets of all of saidtubes and a second tubular doughnut ring connecting the outlets of allof said tubes, an inlet for fluid to be heated connected to said firsttubular doughnut ring and an outlet for fluid to be heated connected tosaid second tubular doughnut ring.

7. A fuel fired heat exchanger as claimed in claim 6 including meansforming an exhaust outlet passage for products of combustion, said meanslocated in said annular air passage adjacent to said heat insulatingmember and provided with inlets opening into the annular outer heatexchange chamber and an outlet opening outwardly of said shell.

8. A heat exchanger as claimed in claim 1 including an exhaustpassage-forming ring carried by said shell adjacent to the fuel inlet,said shell having an exhaust outlet opening therein opening from saidheat exchange chamber into said exhaust passage-forming ring, wherebyproducts of combustion will travel in one direction throughout saidcombustion chamber and in a reverse direction throughout said heatexchange space to said exhaust outlet.

9. In a fuel fired heat exchanger, a shell, an annular partition in saidshell forming an inner combustion chamber and an outer annular chamberabout said combustion chamber, a heat insulation element spaced inwardlyof one end of said shell to form an annular air passage space anddisposed to close the end of said annular partition adjacent thereto,said heat insulation element provided with an air inlet passage openinginto said combustion chamber at' one end and in communication with saidannular air passage space atthe other end, a second annular partition insaid shell about said outer annular chamber formingan air passage withsaid shell, said second annularpartition defining an openingto providecommunication between said air passage and said annular air passagespace, said shell having an air inlet communicatingwith said partitionformed air passage, said first mentioned annular partition having anopening therein spaced from said air inlet to provide communicationbetween said inner combustion chamber and said outer annular chamber, aninlet for fuel gas opening into said combustion chamber, a plurality ofsubstantially U-shapedtubes having their ends extending through saidfirst-named annular partition and their spaced legs located in saidcombustion chamber and said annular outer chamber, said shell having'anoutlet for gases of combustion therein opening into said outer annularchamber, inlet means for fluid to be heated connected to the inlet endsof said substantially U-shaped tubes and outlet means for fluid tobe'heated connected to the outlet ends of substantially U-shaped tubes.

10. In a heat exchanger, a shell, a pair of spaced transverse partitionsin said shell intermediate its ends and forming an intermediate chamberand heat exchange chambers 'on each side of each intermediate chamber, acentrally located annular partition in said intermediate chamber forminga central passageway, a transverse partition in said intermediatechamber outwardly of said central annular partition and'forming an inletpassage and an outlet passage, a plurality of tubes in one of said heatexchangeehambers and having their inlets communicating with said inletpassage and their outlets communicating with said central passage, and aplurality of tubes in the other of said heat exchange chambers havingtheir inlets communicating with said central passage and their outletscommunicating with said outlet passage inlet means for fluid to beheated communicating with said inlet passage,"and outlet means for thefluid to be heated communicating with said outlet passage.

11. A heat exchanger as claimed in claim wherein one of said heatex'change'ehambers forms a combustion chamber, an inlet for air to saidcombustion chamber, an inlet for fuel gas to the combustion chamber,said shell provided with an outlet for combustion gases communicatingwith said combustion chamber, and means for igniting fuel gas in saidcombustion chamber.

12. A heat exchanger as claimed in claim 10 wherein one of said heatexchange chambers forms a combustion chamber, an inlet for air'to saidcombustion chamber, an inlet for fuel gas to the combustion chamber,means for igniting fuel gas in said combustion chamber and saidshellprovided with an outlet for gases of combustion communicating withsaid combustion chamber, an inlet pipe for a heating medium extendingfrom one end of the shell into the other of said heat exchange chambersfor directing incoming heating medium into the chamber about the tubesthereinat a point near one of said transverse-partitions, an outletforthe heating medium, and means for directing the heating mediumlongitudinally'along the "tubes from the point of inlet to said outlet.

13. A heat exchanger as claimed in claim 10 wherein an annular partitionis located in each of said heat exchange chambers, andwherein said tubesare substantially U shaped with their bends extending through theannular partitions in the heat exchange chambers and with the legportions of the U-shaped tubes located one on each side of said annularpartitions, the inlet ends of the substantially U-shaped tubes in one ofsaid heat exchange chambers communicating .with said inlet passage andth'eir outlet ends communicatingwith said central passage; the --inl et-1endsofsaid substantially-- U -shapd 'tubes in the *ot-h'e'r ofsaidheafexchange chambers communicating with "said central passage andtheir'outlet ends communicating with said outlet passage.

14. 5 A fuel fired-heat exehanger as claimed in claim 10 wherein a blockisrnounted in the end of one of said heat exchangers remote from said'intermediate chamber, a first annularpartition insaid block containingheat exchange chamber and engaging-saidbloek to form an inner combustionchamber andan outer heat exchange space in the chamber, an air inlet forsaid combustion chamber, an inlet for fuelgas to the combustion chamber,means for igniting fuel gas in said combustion chamber, said shellprovided with an outlet for gases of combustion communicating withsaid'heat exchange chamber, and said annularpartition having openingstherein to allow combustion gases to pass from said inner combustionchamber to said outer heat exchange space in the block containing heatexchange chamber.

15. A fuelfire heat exchanger-as claimed in claim 10 wherein a block ismounted in the end of one of said heat exchange chambers remote fromsaid intermediate chamber, a first annular partition in said blockcontaining heat exchange chamber and engaging said block to form aninner combustion chamber and an outer heat exchange space in the blockcontaining heat exchange chamber, a second annular partition in saidblock containing heat exchange chamber forming an annular air chamberabout said heat exchange space, an air inlet to said annular chamber,said block shaped to provide an annular air passage having inletcommunication with said air chamber and outlet communieationwith saidcombustion chamber, an inlet for fuel gas to said combustion chamber,means for igniting fuel gas in said combustion chamber, said shellprovided with an outlet for combustion gases communicating with saidheat exchange space, and said first annular partition havingopeningstherein to allow combustion gases to pass from said combustion chamberinto said outer heat exchange space in said block containing heatexchange chamber.

16. A fuel fired heat exchanger as claimed in claim 10 wherein a blockis mounted in the end of one of said heat exchange chambers remote fromsaid intermediate chamber, a first annular partition in said blockcontaining heat exchange chamber and engaging said block to form aninner combustion chamber and an outer heat exchange space in thechamber, a second annular partition in said block containingheatexchange chamber forming an annular air chamber about said heatexchange space, an air inlet to said annular air chamber, said blockshaped to provide an annular air passage having inlet communication withsaid air chamber and outlet communication with said combustion chamber,an inlet for fuel gas to said combustion chamber, means for ignitingfuel gas in said combustion chamber, means forming an exhaust outletpassage for products of combustion, said means located in said airchamber adjacent the block carrying end of the heat exchange chamber andprovided with inlets opening into the heat exchange space and withoutlets opening outwardly of said shell, and said first partitionprovided with openings therein at its end remote from said block wherebyproducts of combustion flow from the combustion chamber into and throughsaid heat exchange space of the block containing heat exchange chamber.

References Cited inthe file of this patent UNITED STATES PATENTS

1. IN A FUEL FIRED HEAT EXCHANGER, A SHELL HAVING AN INLET FORCOMBUSTIBLE FUEL AT ONE END THEREOF, AN ANNULAR PARTITION IN SAID SHELLFORMING AN INNER COMBUSTION CHAMBER AND AN ANNULAR OUTER HEAT EXCHANGECHAMBER, SAID INLET FOR COMBUSTIBLE MATERIAL COMMUNICATING WITH SAIDINNER COMBUSTION CHAMBER, SAID ANNULAR PARTITION HAVING OPENINGS THEREINNEAR THE END OF THE SHELL REMOTE FROM SAID FUEL INLET, A PLURALITY OFSUBSTANTIALLY U-SHAPED TUBES IN SAID SHELL AND HAVING THEIR INLETS ANDOUTLETS AT THE ENDS OF THE SHELL REMOTE FROM SAID FUEL INLET, THE BENDSOF SAID TUBES EXTENDING THROUGH SAID ANNULAR PARTITION WHEREBY ONE LEGOF EACH OF THE TUBES WILL BE LOCATED IN SAID INNER COMBUSTION CHAMBERAND THE OTHER LEG OF EACH TUBE WILL BE LOCATED IN THE OUTER ANNULAR HEATEXCHANGE CHAMBER SAID SHELL HAVING AN OUTLET FOR GASES OF COMBUSTIONTHEREIN, SAID OUTLET OPENING INTO SAID HEAT EXCHANGE CHAMBER ADJACENT TOTHE END OF THE SHELL REMOTE FROM SAID OPENINGS IN SAID ANNULARPARTITION.